Vision systems used to inspect the quality of manufactured components are becoming more prevalent in industrial settings to ensure the quality of the manufactured product. For example, composite materials used in aerospace for reducing weight of an airplane require a high degree of integrity. There is an unrealized desire to inspect the fiber orientation and placement of carbon fiber material used in the construction of these aerospace components using a vision system from a distance. Additionally, weld quality, dimensional stability, and other areas of manufactured products that require a quality inspection are increasingly monitored by way of a vision system or assembly. A typical vision system consists of camera and lens assembly which can generally image a wide field of view at low resolution, for example using a wide angle lens, or a narrow field of view at high resolution, for example, using a telephoto lens precisely focused on a specific area of interest. However, applications such as imaging a large aerospace component at a level sufficient to resolve fibers used in the material, requires high resolution and a wide field of view to encompass the large scale of the component, which reduces resolution to level making a vision system of this type impractical. One attempt to address the limitations of these systems is by the vision system assembly using galvanometer scanning mirrors generally shown at 10 of FIG. 1. A camera 12 is orientated so that its field of view 14 is directed toward a first mirror 16, which directs the field of view 14 toward a second mirror 18, and subsequently onto a workpiece 20.
An angular orientation of the first mirror 16 relative to the field of view 14 of the camera 12 is controlled by a first galvanometer 22. In a like manner, an angular orientation of the second mirror 18 relative to the field of view 14 of the camera 12 is controlled by a second galvanometer 24.
This arrangement combined with appropriate selection of the camera resolution and lens field of view can provide arbitrary levels of theoretical resolution. For example, a telephoto lens can be selected such that the resolution of a single element of a high resolution camera sensor can correspond to a few thousandths of an inch resolution over entire parts spanning multiple feet. However, this sensor spatial resolution is ineffective if the image on the sensor is not precisely focused and is blurred across a large number of pixels on the sensor rendering this alternative impractical for the types of applications that would be most benefitted. A further problem with this arrangement is that focusing the camera 12 upon, in particular, a three-dimensional surface has proven slow, rendering this type of arrangement inefficient in a rapid manufacturing process. Although the galvanometers are known to move the field of view 14 of the camera 12 in a two-dimensional (X,Y) environment, the focus of the camera 12 is ineffective in a three-dimensional environment. This type of arrangement is generally disclosed in U.S. Pat. No. 5,615,013 to the same inventor of the present application, the content of which is incorporated herein by reference.
FIG. 2 shows an attempt to adjust the focus of the camera 12 in a three-dimensional direction making use of a similar galvanometer and mirror arrangement. In this arrangement, a CCD or CMOS the sensor array 26 is used to capture an image along the field of view 14 of the camera. A lens 28 is moved along an axis a of the field of view 14 of the camera 12 by way of a translation mechanism 30. However, the translation mechanism 30 used to move the lens 28 to enhance image clarity along a z axis of a three-dimensional surface is exceedingly costly and too slow to meet the demands of modern manufacturing systems. Additionally, the lens translation mechanism 30 is cumbersome and cannot be packaged into a small area. Furthermore, any deviations in the position of the lens from the axis of translation, even by a distance of microns, produces an offset in the imaged position generated by camera 12, making accurate measurements impossible. Therefore, it would be desirable to provide a more consistently accurate, rapid and cost-efficient method to generate a high resolution image along three axis of a workpiece.